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arXiv · 2303.17850

Singular flat bands in the modified Haldane-Dice model

Alexander Filusch·Holger Fehske
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Abstract

Flat bands can be divided into singular and non-singular ones according to the behavior of their Bloch wave function around band-crossing points in momentum space. We analyze the flat band in the Dice model, which can be tuned by a uniaxial strain in the zigzag direction and a Haldane-type next-nearest neighbor interaction, and derive the topological phase diagram of the modified Haldane-Dice model to obtain all band-gap closings with the central band. When the central band is flat, we determine its compact localized state and classify its behavior at all band-touching points by means of the Hilbert-Schmidt quantum distance. We find that the flat band remains singular for all band-touching points (topological phase transitions) with a maximal quantum distance and give expressions for the resulting non-contractible loop states on the real-space torus.

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Alexander Filusch, Holger Fehske. 2023-03-31. Singular flat bands in the modified Haldane-Dice model. https://doi.org/10.1016/j.physb.2023.414848

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